The invention relates to a resectoscope of the type including a main body carrying a tubular shaft, an optical guide plate arranged at a fixed distance proximally of the main body, a sliding body longitudinally movably guided between the main body and the optical guide plate and a spring bridge comprising two levers, which are pivotally connected together at one end and are acted on by a spring and the other ends of which are pivotally connected to the sliding body on the one hand and to the optical guide plate or to the main body on the other hand.
Urological resectoscopes of the standard construction which is now usual have an endoscope optical system, which extends through the entire resectoscope including the tubular shaft, and an electrode, generally constructed as a cutting blade, which is longitudinally movably arranged in the region distally in front of the optical system. The electrode is moved by means of an elongate electrode carrier, which projects proximally beyond the region of the tubular shaft and is secured to the sliding body and is electrically connected to the electrode and an electrical power supply. The operator moves the sliding body on the proximal portion of the resectoscope and thus the electrode to produce cutting movements.
In most known resectoscopes, the sliding body is moved against the force of a spring. Several variants are possible in which the sliding body is either pulled back in the proximal direction against the force of a spring or is advanced distally against the force of a spring and then returns automatically under the force of the spring. Finger grip members for actuation can be secured to the main body and to the sliding body or to the sliding body and to the optical system guide plate, depending on the construction. The spring can, depending on the variant referred to above and depending on whether the spring is a compression spring or a tension spring, also be provided between the main body and sliding body or between the sliding body and optical system guide plate. Leaf springs, for instance, are common as the springs.
In resectoscopes of the type referred to above, the spring is constructed in the form of a spring bridge comprising levers and joints. Such a construction is shown in FIG. 21 of U.S. Pat. No. 5,088,998. The two levers are pivotally connected together at a distance from one another by means of two joints on a shaft. Also provided is a spring which urges the two levers apart. The free ends of the two levers are pivotally connected by means of a respective joint centrally beneath the shaft of the resectoscope to the main body on the one hand and to the sliding body on the other hand. The spring bridge is situated beneath the resectoscope in this construction.
A further construction of the type referred to above is shown in the brochure xe2x80x9cThe Next Step in Resectoscope Technologyxe2x80x9d from the company Olympus Optical Co. Ltd. dated 1998. The spring bridge is provided in this case above the resectoscope between the sliding body on the one hand and the optical system guide plate on the other hand. In distinction to the construction referred to above, the free ends of the levers laterally engage two bearing points, which are opposed to one another with respect to the optical system, which ensures good rotational stabilisation of the sliding body and makes more expensive sliding guides, as in the construction referred to above, unnecessary.
The spring bridges in the prior art are constructionally very expensive and require very exact mountings in order, in particular, to make the necessary rotational stability possible. The problem of rotational stability is solved in a considerably better manner by the second known construction referred to above. However, a disadvantage of this construction is the mounting of the spring bridge both on the sliding body and also on the optical guide plate with two lateral bearings in each case. The spring bridge is thus mounted on the resectoscope with four bearings which results in a redundancy. If the bearings are machined very precisely in the necessary manner, they tend to jam, which is extremely disadvantageous for precise, sensitive actuation of the resectoscope. Of disadvantage with this known construction are also the high manufacturing costs of the spring bridge with a total of six bearings and also its other constructional expense and its high weight.
The object of the invention is to simplify a resectoscope of the type referred to above structurally and as regards manufacture as regards the construction of the spring bridge to provide good guiding characteristics and to reduce its weight and to produce a construction which does not tend to jam.
According to the present invention the other end of one of the levers is pivotally connected on only one side of the resectoscope.
In the construction in accordance with the invention, one of the levers engages the resectoscope only on one side. The spring bridge thus engages the resectoscope only with a maximum of three bearings. The redundancy and thus the danger of jamming is, therefore, completely avoided, even with highly precisely fabricated bearings and the construction is simplified. As a result of the reduced number of bearings, the manufacturing and, in particular, the assembly costs are reduced. A resectoscope is produced which may be operated very easily and sensitively with a high stability of guiding, particularly also as regards rotational guidance.
In one embodiment, the other lever is pivotally connected only to the opposite side of resectoscope. Thus both levers are mounted on the resectoscope only on one side, namely on opposite sides. The spring bridge is thus considerably simplified. In particular, both levers may be of the same construction, which reduces the costs.
The two levers could be directly pivotally connected to one another using only one bearing. Advantageously, however, the connected ends of the two levers are pivotally connected to a common shaft and are laterally spaced apart. The proven mode of construction in accordance with the prior art is thus adopted at this position.
The levers may have bearings at their ends and be in the form of rods between the bearings. This mode of construction, which is possible with the present invention, simplifies and facilitates the construction of the levers.
The levers can be inherently straight. Advantageously, however, the other ends of the two levers are constituted by bent portions inclined to the remainder of the lever, the two bent portions being bent in the proximal direction and the distal direction, respectively. The positions of the bearing points may thus be altered in a desired manner. As a result of the bent configuration of the free ends, a better kinematics of the guidance is produced with a higher tilting stability. Rattling as a result of clearances that are present is also prevented.
It is provided in one embodiment that arranged on the optical guide plate there is a distally extending projection to which one of the levers is pivotally connected and which engages in a recess in the sliding body. The bearings at the ends of the free levers may thus be arranged precisely opposite one another with respect to the shaft of the resectoscope without the sliding travel of the sliding body being shortened.
It is also possible that the other lever is pivotally connected to both sides of the main body or the optical guide plate. In this construction the one lever is mounted on the resectoscope with one bearing and the other lever with two bearings. A construction is thus produced with high guiding stability in which redundancy and thus the risk of jamming is reliably prevented.
Further features and details of the invention will be apparent from the following description of certain specific embodiments which is given by way of example with reference to the accompanying drawings.